Assessment of Gage Length Effects on Cylindrical Austenitic Stainless Steel Fatigue Specimens in Air and High-Temperature Water Environment

Abstract

Abstract This paper addresses the specimen gage length on the fatigue behavior of 316L austenitic stainless steels when tested in air and light water reactor environment. In fatigue testing, the overall spread of the data tends to be high due to high natural random error and also unknown systematic errors arising from ambiguous or poorly constrained standards. Identifying and mitigating sources of systematic error can reduce the high spread in fatigue data and significantly increase the reliability of fatigue life approximations under a specific set of test conditions. In order to reduce sources of systematic error, we have explored the effect of the gage length of 316L stainless steel specimens in two different environments. For this purpose, a minimum of three low-cycle fatigue tests were performed for each set of conditions with 0.3% and 0.6% strain amplitude using gage lengths of 20, 27 and 34 mm. The effect of the high-temperature BWR environment results in a strong reduction of the fatigue life in comparison with tests carried out in air at room temperature. The effect is usually quantified in literature using the Fen factor defined as the ratio of the fatigue life in air at room temperature to the fatigue life in a light water reactor (LWR) environment. Fen factors were calculated for each set of conditions and specimen gage lengths using room temperature air tests as reference and compared with existing literature.